During well completion, casing is emplaced in a wellbore. Drilling mud and/or spacer fluids are initially in place in an annulus region between casing and formation. As the cement slurry is pumped through the casing and into the annulus between the casing and the formation, the cement slurry displaces the spacer fluid, which in turn, displaces the drilling mud. The contamination of cement with drilling mud or spacer fluid can have significant negative consequences for the curing and integrity of the cement, and can provide potential conduits for flow behind casing.
Cement can be interrogated via various wireline-deployed through-casing resistivity (TCR) methods after the cement was emplaced in the annulus region between the casing and formation. However, the TCR methods have a number of deficiencies, such as significant signal attenuation through casing. Moreover, TCR methods require access to the well, and thus cannot be deployed in real-time as the cement slurry is being pumped into the well. Variety of distributed fiber optic sensing methods (e.g., based on monitoring acoustics, temperature, pressure, and the like) were also proposed for cement slurry monitoring. However, accuracy of these fiber optic sensing methods is often unsatisfactory.
Therefore, it is desirable to efficiently and accurately monitor the quality of cementation process during and after cement placement in the wellbore.